1. Field of the Invention
The instant disclosure relates to a fan motor control device; more particularly, to a fan motor control device for controlling the soft start of the fan motor.
2. Description of Related Art
A circuit diagram for a conventional fan motor control device 1 is shown in FIG. 1. The fan motor control device 1 normally employs a controller 10 to drive a fan motor 12. The controller 10 may be an integrated circuit (IC) unit having different pins for connecting to a Hall device 14, a converter 16, and other electric circuits. The Hall device 14 is assigned to detect the operation status of the fan motor 12 and generate instantaneous feedback signal (not shown) to the controller 10.
A controlled terminal VTH of the controller 10 receives an input voltage signal V1 from the converter 16. For the lowest rotational speed (also called speed of revolution), the controller 10 has a lowest rotational speed setup terminal RMI for receiving a lowest rotational speed threshold voltage V2 from an external circuit 15. Once powered up, the controller 10 would normally control the fan motor 12 speed based on the magnitude of the input voltage signal V1.
Thereby, during the initial start-up, the controller 10 would consume more power. Plus, the controller 10 would be subjected to higher starting current. The impact of high starting current tends to reduce the service life of the controller 10. In addition, as the fan motor speed picks up immediately once the controller 10 is powered up, excessive fan noise can be heard.